1. Field of the Invention
This invention concerns an ignition system which is particularly applicable to a diesel type engine that employs spark assist. The designation diesel type engine is intended to include a fuel injection system where the fuel pressure acts to lift the fuel injection valves.
2. Description of the Prior Art
Heretofore, a system has been disclosed for employing a fuel injection valve to generate an electrical signal in order to control an ignition signal that is applied to the cylinder related to each such fuel valve. That system is disclosed in U.S. Pat. No. 4,066,059 issued Jan. 3, 1978 and assigned to the same assignee as this application. The ignition system in that patent makes use of direct amplification of the injection valve initiated signal in order to control the generation of a high voltage spark signal. Furthermore, the injection valve employed in that patent requires special electrical insulating material elements to isolate the valve needle, or plunger from the body of the valve except where it touches the valve seat when closed.
Another known suggestion was related to using a fuel injection needle valve to act as a switch for operating test equipment in order to monitor a fuel injection nozzle. That arrangement is disclosed in U.S. Pat. No. 3,942,366, issued Mar. 9, 1976. However, the electrical switch structure is separate from the valve plunger and seat, so that special valve and switch structures are involved which add cost to the ordinary valve construction.
Consequently, it is an object of this invention to provide a system for generating a signal to control a spark voltage for an internal combustion engine which signal originates at the injector valve of ordinary construction when the fuel pressure lifts the valve plunger.
Another object of this invention is to provide an electrical ignition system which can develop a clean ignition initiating spark signal that has a desired duration for each spark, and that overcomes the drawbacks in connection with the foregoing prior art.